Stabilization of Therapeutic Agents to Facilitate Administration

ABSTRACT

The present invention provides for a carrier complex for administration of therapeutic agents. In one aspect, an isolated  C. botulinum  carrier complex is provided, where the carrier complex lacks a native neurotoxin subunit.

BACKGROUND

This is a national stage application under 35 U.S.C. §371 of PCT patentapplication PCT/US2010/060402, filed on Dec. 15, 2010, which claims thebenefit of U.S. Provisional Patent Application No. 61/287,850 filed Dec.18, 2009, each of which is hereby incorporated by reference in itsentirety.

The present disclosure relates to non-neurotoxin subunits of botulinumneurotoxin complexes, as utilized as a carrier for therapeutic agents.Botulinum toxins are proteins produced by the anaerobic bacteriumClostridium botulinum. There are seven immunologically distinctbotulinum neurotoxins, which are designated botulinum neurotoxinserotypes A through G. Each complex consists of a neurotoxin subunit, anon-toxin non-hemagglutinin subunit and hemagglutinin subunits ofvarious sizes and number, depending upon the serotype. The botulinumneurotoxin serotypes vary in the animal species they affect and theseverity and duration of paralysis they evoke. The resultingneuroparalytic illness is referred to as botulism. See Preparation andCharacterization of Botulinum Toxin Type A For Human Treatment, Schantz,E. J., et al, Therapy with Botulinum Toxin, 1994; v.25: pp 41-49.

Botulism, or botulinum poisoning, can be caused by exposure to C.botulinum, which can grow in improperly sterilized and sealed foods orfrom botulinum spores, which are commonly found in soil. Symptoms ofbotulinum poisoning typically appear 18 to 36 hours after exposure tothe bacterium or its spores. Botulinum toxin can pass unattenuatedthrough the lining of the gut and can attack peripheral motor neurons.Symptoms of botulinum poisoning can include difficulty walking,swallowing, speaking, or in more extreme cases, death can result due toparalysis of respiratory muscles. Schantz, E. J. et al., Properties anduse of Botulinum Toxin and Other Microbial Neurotoxins in Medicine,Microbiological Reviews, 1992 March, v.1:pp 80-99.

While passing through the digestive tract, the hydrophobically-boundnon-toxin subunits are thought to stabilize and protect the neurotoxinsubunit. Protection is especially important for the toxin to passthrough the low-pH portions of the digestive tract, which couldotherwise denature the neurotoxin subunit. See Preparation andCharacterization of Botulinum Toxin Type A For Human Treatment, Schantz,E. J., et al, Therapy with Botulinum Toxin, 1994; v.25: pp 41-49.

Once the botulinum complex reaches the target neuron, the neurotoxinsubunit disassociates from the remaining complex subunits and binds tothe presynaptic membrane of the target neuron. The neurotoxin subunitbinds to a cell surface receptor and is engulfed via receptor mediatedendocytosis. The neurotoxin subunit, which is about 150 kDa, iscomprised of a 100 kDa heavy chain portion and a 50 kDa light chainportion, the two portions linked by a disulfide bridge. The 100 kDaheavy chain enables the light chain to bind to the presynaptic membraneof the nerve cell and facilitates the transmembrane transfer of thelight chain into the cytoplasm of the cell. The 50 kDa light chain isresponsible for the inhibition of acetylcholine release. See Preparationand Characterization of Botulinum Toxin Type A For Human Treatment,Schantz, E. J., et al, Therapy with Botulinum Toxin, 1994; v.25: pp41-49.

Once the neurotoxin translocates through an endosomal membrane andenters the cytoplasm of the neuron, the light chain inhibits the releaseof acetylcholine, which interrupts signals normally transmitted from thenerve cell to neighboring muscle tissue. The result is local paralysisand relaxation of muscle tissue associated with the nerve cell.

Botulinum toxins have been used in the treatment of variousneuromuscular disorders and conditions involving muscle spasm, as wellas hyperhydrosis, cervical dystonia and blepharospasm.

Botulinum toxin is obtained by growing cultures of C. botulinum in afermenter under anaerobic conditions, followed by harvesting andpurifying the fermented mixture in accordance with known techniques toobtain the botulinum neurotoxin complex.

The protective and stabilizing effects provided by the non-toxinsubunits can be useful to facilitate the enteric administration of othertherapeutic agents that cannot withstand the extreme conditions of thehuman digestive tract, or to stabilize a therapeutic agent administeredby other routes, such as intramuscular or subcutaneous injection, forexample.

The present invention meets this need and provides for a carrier complexfor administration of therapeutic agents. In one aspect, an isolated C.botulinum carrier complex, where the carrier complex lacks a nativeneurotoxin subunit, is provided.

DESCRIPTION

As used herein, the words or terms set forth below have the followingdefinitions.

“About” means that the item, parameter or term so qualified encompassesa range plus or minus ten percent above and below the value of thestated item, parameter or term.

“Botulinum toxin” means a neurotoxin produced by C. botulinum andencompasses the botulinum toxin serotypes A, B, C, D, E, F and G.

A “carrier complex” means an association of at least two non-toxinprotein subunits that form a complex, devoid of a native neurotoxinsubunit.

A “native neurotoxin subunit” means the neurotoxin subunit naturallyoccurring (i.e. wild type) in a Botulinum toxin complex produced by C.botulinum bacteria.

As used here, the term “complex” refers to at least two non-toxinprotein subunits, wherein the non-toxin protein subunits can be nativeor variant.

A “multi-subunit complex” means the association of proteins naturallyproduced by C. botulinum bacteria consisting of a neurotoxin subunit, anon-toxin non-hemagglutinin subunit and various hemagglutinin subunits.

An “open conformation” means the three-dimensional arrangement of thenon-toxin subunit of a carrier complex which allows for the release of anative neurotoxin subunit, for example, or the addition and/or releaseof a therapeutic agent, while the non-toxin protein subunits maintaintheir association with each other.

A “closed conformation” means the three-dimensional arrangement of thenon-toxin subunits of the carrier complex which does not allow for theremoval of a neurotoxin subunit, or does not allow for the additionand/or release of a therapeutic agent, while the non-toxin proteinsubunits maintain their association with each other.

A “non-native therapeutic molecule” or a “non-native therapeutic agent”means a molecule or agent other than the native neurotoxin subunit thatis naturally produced by C. botulinum.

A “modified multi-subunit complex” means a complex not naturallyproduced by C. botulinum, such as that produced by genetic engineeringtechniques.

A “non-native neurotoxin subunit” means a modified or recombinantneurotoxin molecule not naturally produced by C. botulinum.

“Naturally produced” means wild type.

A “therapeutic agent” or a “therapeutic molecule” is a molecule/agentthat is biologically active or pharmaceutically active.

“Pharmaceutically active” means a chemically derived molecule or a smallmolecule that exhibits a desired and beneficial result or affect.

“Biologically active” means a non chemically derived molecule or abiologic that exhibits a desired and beneficial result or effect andthat could be obtained from an organism. The organism can be, forexample, a bacterium, yeast, etc.

A “modified organism” means one that is not naturally occurring, butwhich exists as the result of a directed change to the organism'sgenetic composition arising from the use of genetic engineeringtechniques.

A “non-native binding moiety” means a binding moiety of a botulinumneurotoxin that arises as a result of genetic engineering techniques.

A “modified C. botulinum bacterium” means a non-native form of C.botulinum bacterium, wherein at least one of its nucleic acids has beendeleted, modified or replaced, as compared to a native or wild type C.botulinum bacterium.

A “non-native host” means a bacterium that does not naturally producethe proteins of the carrier complex.

A “recombinant multi-subunit complex” means a protein complex notnaturally produced by C. botulinum and arising as a result of geneticengineering techniques. A recombinant multi-subunit complex can producedin a C. botulinum or a non C. botulinum bacterium.

“Variant” means that which is not native or naturally occurring.

A “ligand” means a binding element that can be attached to a carriercomplex or a therapeutic molecule or agent for targeting/preferentialbinding purposes.

A “substrate” is a substance that can selectively bind to a ligand.

In one embodiment of the invention, the non-toxin subunits of thebotulinum neurotoxin complex are utilized as a carrier complex for atherapeutic agent, wherein it is understood that the therapeutic agentdoes not include the native (i.e. a wild type) botulinum neurotoxinsubunit naturally associated/produced with wild type non-toxin subunits(types and numbers).

In another embodiment of the invention, the multi-subunit complexproduced by a C. botulinum bacterium is isolated and the 150 kDaneurotoxin subunit is removed, while the non-toxin subunits maintainassociation with each other. Once the neurotoxin subunit has beenremoved, a non-native therapeutic agent can be added to the carriercomplex and retained by various molecular forces, as disclosed herein.

As utilized herein, a botulinum neurotoxin can be selected from thegroup consisting of botulinum toxin serotype A, B, C, D, E, F and G.

In another embodiment of the invention, a ligand can be joined andretained by the carrier complex by various molecular forces, asdisclosed herein.

In another embodiment of the invention, a ligand and a therapeutic agentare joined together, and then joined to the carrier complex.

In another embodiment of the invention, a ligand and a therapeutic agentare individually joined to the carrier complex.

In yet another embodiment of the invention, a recombinant multi-subunitcomplex produced by a C. botulinum is isolated and the 150 kDa toxinsubunit is removed, while the non-toxin subunits maintain associationwith each other. Once the neurotoxin subunit has been removed, anon-native therapeutic agent can be joined to/retained by the carriercomplex by various molecular forces, as disclosed herein.

In another embodiment of the invention, the multi-subunit complexproduced by a Clostridium botulinum is isolated and the subunits arecompletely disassociated from one another in solution. The neurotoxinsubunit is then removed from solution and the remaining subunitsproperly reassociate relative to each other to form the carrier complex.Once the remaining non-toxin subunits reassociate, a non-nativetherapeutic agent can be joined to the complex by various molecularforces, as disclosed herein.

In another embodiment of the invention, the carrier complex is producedby a modified organism that does not produce a neurotoxin subunit. Inyet another embodiment of the invention, the modified organism alsoproduces a therapeutic agent in addition to the non-toxin subunits thatmake up the carrier complex. In a particular embodiment of theinvention, the modified organism is a C. botulinum bacterium that doesnot produce a neurotoxin subunit or the organism can be another microbe,such as E. coli or yeast.

In one aspect, a method of obtaining the carrier complex is providedthat includes isolating the multi-subunit complex in solution, followedby increasing the pH of the solution to about 9 to induce an openconformation, resulting in release of the neurotoxin subunit from themulti-subunit complex to thereby provide a carrier complex. In oneembodiment, removal of the neurotoxin subunit from solution is achievedchromatographically by utilizing a cation exchange column, for example,and subsequently lowering the pH of the resulting eluent to about pH 6to induce a closed conformation of the carrier complex.

In one embodiment of the invention, the method further comprises theaddition of a therapeutic agent and/or a ligand to the carrier complex.

An embodiment of the invention comprises an isolated C. botulinumcarrier complex, wherein the carrier complex lacks a native neurotoxinsubunit and said carrier complex is capable of reversibly andcontrollably alternating between an open and a closed conformation. Anembodiment can further comprise a non-native therapeutic molecule, or aligand, or a therapeutic agent and a ligand. In some embodiments thecarrier complex is a variant carrier complex, or a non-nativetherapeutic molecule, or a non-toxin non hemagglutinin subunit and anon-toxin hemagglutinin subunit. Some embodiments can further comprise anon-native neurotoxin subunit, or a non-toxin non hemagglutinin subunitand a non-toxin hemagglutinin subunit. In certain embodiments thenon-native therapeutic molecule is a pharmaceutically active orbiologically active molecule. In some embodiments the non-nativetherapeutic molecule is covalently associated with the complex, or isassociated to the complex through hydrophobic interactions, or isassociated to the carrier complex with ionic bonds, or is associated tothe carrier complex with hydrogen bonds, or is associated to the carriercomplex with Van der Waals interactions.

In certain embodiments the non-native therapeutic molecule is apharmaceutically active or biologically active molecule, which can becovalently associated with the carrier complex, or associated with thecomplex through hydrophobic interactions, or associated with the carriercomplex with ionic bonds, or associated to the carrier complex withhydrogen bonds, or is associated to the carrier complex with Van derWaals interactions.

Certain embodiments can comprise an isolated C. botulinum carriercomplex of approximately 750 kDa, comprising a non-toxin nonhemagglutinin subunit, an approximately 48 kDa non-toxin hemagglutininsubunit, an approximately 33 kDa non-toxin hemagglutinin subunit, anapproximately 20 kDa non-toxin hemagglutinin subunit, an approximately17 kDa non-toxin hemagglutinin subunit, and wherein the isolated carriercomplex lacks a native neurotoxin subunit.

Certain embodiments can comprise an isolated C. botulinum carriercomplex of approximately 500 kDa, comprising a non-toxin nonhemagglutinin subunit, an approximately 70 kDa non-toxin hemagglutininsubunit, an approximately 33 kDa non-toxin hemagglutinin subunit, and anapproximately 17 kDa non-toxin hemagglutinin subunit, wherein theisolated carrier complex lacks a native neurotoxin subunit.

Certain embodiments of the invention can comprise an isolated C.botulinum carrier complex of approximately 350 kDa, comprising anon-toxin non hemagglutinin subunit, an approximately 53 kDa non-toxinhemagglutinin subunit, an approximately 33 kDa non-toxin hemagglutininsubunit, an approximately 17 kDa non-toxin hemagglutinin subunit, and anapproximately 22 kDa non-toxin hemagglutinin subunit, wherein theisolated carrier complex lacks a native neurotoxin subunit.

Certain embodiments of the invention can comprise an isolated C.botulinum carrier complex of approximately 350 kDa, comprising anon-toxin non hemagglutinin subunit, an approximately 70 kDa non-toxinhemagglutinin subunit, an approximately 33 kDa non-toxin hemagglutininsubunit, and an approximately 17 kDa non-toxin hemagglutinin subunit,wherein the isolated carrier complex lacks a native neurotoxin subunit.

Embodiments of the invention include a stabilized therapeutic molecule,comprising an isolated C. botulinum neurotoxin carrier complex, whereina neurotoxin subunit has been removed, and a therapeutic molecule,wherein the therapeutic molecule is a non-native therapeutic molecule.In some embodiments the therapeutic molecule is a non-native therapeuticmolecule, such as, for example, insulin.

Some embodiments include a modified organism producing a carriercomplex, said carrier complex comprising a non-toxin non hemagglutininsubunit and a non-toxin hemagglutinin subunit, wherein said carriercomplex lacks a neurotoxin subunit. In certain embodiments the carriercomplex further comprises a non-native neurotoxin subunit having anon-native binding moiety.

Embodiments of the invention include a modified C. botulinum bacteriaexpressing a variant carrier complex, wherein the variant carriercomplex lacks a neurotoxin subunit.

Some embodiments of the invention include a method of purifying acarrier complex derived from C. botulinum, the carrier complex lacking anative botulinum neurotoxin subunit, comprising isolating a nativemulti-subunit complex, disassociating the native multi-subunit complexinto its constituent subunits, separating the native botulinumneurotoxin subunit therefrom, and re-associating remaining subunits intothe carrier complex, thereby producing a carrier complex lacking anative botulinum neurotoxin subunit. Certain embodiments include thecarrier complex thereby purified. Certain embodiments include the stepof associating a non-native therapeutic molecule to the carrier complexcovalently.

Embodiments of the invention include a method of purifying an about 750kDa carrier complex from an about 900 kDa carrier complex comprisingisolating the 900 kDa carrier complex, disassociating the 900 kDacarrier complex into its constituent subunits, separating an about 150kDa neurotoxin subunit therefrom and re-associating remaining subunitsinto the 750 kDa carrier complex, thereby producing a 750 kDa carriercomplex lacking a native botulinum neurotoxin subunit.

Embodiments of the invention include a method of purifying an about 500kDa carrier complex from an about 650 kDa carrier complex comprisingisolating the 650 kDa carrier complex, disassociating the 650 kDacarrier complex into its constituent subunits, separating an about 150kDa neurotoxin subunit therefrom and re-associating remaining subunitsinto the 500 kDa carrier complex, thereby producing a 500 kDa carriercomplex lacking a native botulinum neurotoxin subunit.

Embodiments of the invention include a method of purifying an about 350kDa carrier complex from an about 500 kDa carrier complex comprisingisolating the 500 kDa carrier complex, disassociating the 500 kDacarrier complex into its constituent subunits, separating an about 150kDa neurotoxin subunit therefrom and re-associating remaining subunitsinto the 350 kDa carrier complex, thereby producing a 350 kDa carriercomplex lacking a native botulinum neurotoxin subunit.

Embodiments of the invention include a method of purifying an about 150kDa carrier complex from an about 300 kDa carrier complex comprisingisolating the 300 kDa carrier complex, disassociating the 300 kDacarrier complex into its constituent subunits, separating an about 150kDa neurotoxin subunit therefrom and re-associating remaining subunitsinto the 150 kDa carrier complex, thereby producing a 150 kDa carriercomplex lacking a native botulinum neurotoxin subunit.

Embodiments of the invention include a method of purifying an about 130kDa carrier complex from an about 280 kDa carrier complex comprisingisolating the 280 kDa carrier complex, disassociating the 280 kDacarrier complex into its constituent subunits, separating an about 150kDa neurotoxin subunit therefrom and re-associating remaining subunitsinto the 130 kDa carrier complex, thereby producing a 130 kDa carriercomplex lacking a native botulinum neurotoxin subunit. Additionalembodiments can include associating a non-native therapeutic molecule tothe 750 kDa carrier complex covalently, or associating a non-nativetherapeutic molecule to the 500 kDa carrier complex covalently, orassociating a non-native therapeutic molecule to the 350 kDa carriercomplex covalently, or associating a non-native therapeutic molecule tothe 150 kDa carrier complex covalently, or associating a non-nativetherapeutic molecule to the 130 kDa carrier complex covalently.

In certain embodiments of the invention, the native multi-subunitcomplex is derived from C. botulinum Type A, C. botulinum Type B, C.botulinum Type C, C. botulinum Type D, C. botulinum Type E, C. botulinumType F or C. botulinum Type G.

Embodiments of the invention include a method of purifying a variantcarrier complex lacking a neurotoxin subunit, wherein the variantcarrier complex is expressed from a non-native host, comprisingisolating a variant carrier complex, disassociating the variant complexinto its constituent subunits, separating a botulinum neurotoxin subunittherefrom, and re-associating remaining variant complex subunits intothe variant carrier complex, thereby producing the variant carriercomplex lacking a neurotoxin subunit expressed from a non-native host,wherein the variant carrier complex is capable of reversibly andcontrollably alternating between an open and a closed conformation.Certain embodiments can include covalently associating the carriercomplex lacking a botulinum neurotoxin subunit to a non-nativetherapeutic molecule, or associating the carrier complex lacking abotulinum neurotoxin subunit to a non-native therapeutic moleculethrough hydrophobic interactions, or ionically associating the complexto a non-native therapeutic molecule.

Embodiments of the invention include a method for stabilizing atherapeutic molecule comprising isolating a C. botulinum carriercomplex, wherein a neurotoxin subunit has been removed and associatingsaid carrier complex with said therapeutic molecule to thereby stabilizesaid therapeutic molecule.

Embodiments of the invention can include a method of purifying a C.botulinum carrier complex devoid of a botulinum neurotoxin subunit,wherein non neurotoxin subunits maintain inter-subunit association,comprising isolating a carrier complex containing a botulinum neurotoxinsubunit and removing the botulinum neurotoxin subunit, thereby producingthe C. botulinum carrier complex devoid of the botulinum neurotoxinsubunit. In certain embodiments the removing step includes raising thepH of a carrier complex containing solution to induce an openconformation of the carrier complex, thereby disassociating thebotulinum neurotoxin subunit from the carrier complex, binding thebotulinum neurotoxin subunit to a substrate to remove the botulinumneurotoxin subunit from the carrier complex containing solution andlowering the pH of the carrier complex containing solution to induce aclosed conformation of the carrier complex, thereby removing thebotulinum neurotoxin subunit. In certain embodiments the C. botulinumcarrier complex is derived from C. botulinum Type A, C. botulinum TypeB, C. botulinum Type C, C. botulinum Type D, C. botulinum Type E, C.botulinum Type F or C. botulinum Type G. In some embodiments thesubstrate is cationic, or anionic, or a hydrophobic substrate, or amixed mode substrate. In some embodiments the subunit components arevariant subunit components and expressed from a non-native host.

Embodiments of the invention include a method of purifying an about 750kDa carrier complex comprising isolating an about 900 kDa carriercomplex and removing an about 150 kDa neurotoxin subunit therefrom,producing the purified the 750 kDa carrier complex, wherein integrity ofthe 750 kDa complex is maintained throughout purification and thecarrier complex is capable of reversible conformational change betweenan open and closed conformation.

Embodiments of the invention include a method of purifying an about 500kDa carrier complex comprising isolating an about 650 kDa carriercomplex and removing an about 150 kDa neurotoxin subunit therefrom,producing the 500 kDa carrier complex, wherein the integrity of the 500kDa complex is maintained throughout purification and the carriercomplex is capable of reversible conformational change between an openand closed conformation.

Embodiments of the invention include a method of purifying an about 350kDa carrier complex comprising isolating an about 500 kDa carriercomplex and removing an about 150 kDa neurotoxin subunit therefrom,producing the 350 kDa carrier complex, wherein the integrity of the 350kDa complex is maintained throughout purification and the carriercomplex is capable of reversible conformational change between an openand closed conformation.

Embodiments of the invention include a method of purifying an about 150kDa carrier complex comprising isolating an about 300 kDa carriercomplex and removing an about 150 kDaZ neurotoxin subunit therefrom,producing the 150 kDa carrier complex, wherein the integrity of the 150kDa complex is maintained throughout purification and the carriercomplex is capable of reversible conformational change between an openand closed conformation.

Embodiments of the invention include a method of purifying an about 130kDa carrier complex comprising isolating an about 280 kDa carriercomplex and removing an about 150 kDa neurotoxin subunit therefrom,producing the 130 kDa carrier complex, wherein the integrity of the 130kDa complex is maintained throughout purification and the carriercomplex is capable of reversible conformational change between an openand closed conformation.

Embodiments of the invention include a method for stabilizing anon-native therapeutic molecule for enteric administration comprisingisolating a carrier complex containing a botulinum neurotoxin subunit,removing the botulinum neurotoxin subunit from the carrier complex andassociating the non-native therapeutic molecule to the carrier complex,thereby stabilizing the non-native therapeutic molecule for entericadministration.

The non-toxin subunits of the multi-subunit complex produced by C.botulinum are thought to protect and stabilize the neurotoxin subunit ofthe complex from unfavorable conditions found in the human digestivetract, including extremely low pH and the presence of proteases andother enzymes that can denature the neurotoxin subunit. If properlyprotected, the neurotoxin subunit will able to function at the targetsite. When the neurotoxin subunit is removed from the multi-subunitcomplex, under proper conditions, the non-toxin subunits can function asand provide a carrier complex for a non-native therapeutic molecule, ora ligand, or both a therapeutic agent and a ligand together, to passthrough the digestive tract, or provide stabilization or protectivefunction for the non-native therapeutic molecule, for example, when thecarrier complex associated with the non-native therapeutic molecule isinjected locally to a target site. This allows the non-nativetherapeutic agent to function at its target site where it will exert itseffect, while the carrier complex provided in accordance with theteachings of the present disclosure provide increasedprotection/stability to the non-native therapeutic agent than ifadministered alone (i.e. non-native therapeutic agent withoutassociation to the carrier complex).

The carrier complex is capable of reversibly and controllablyalternating between an open and closed conformation. The openconformation allows for the non-toxin subunits to maintain associationwith one another while allowing the neurotoxin subunit to be removed andreplaced with a non-native therapeutic agent and/or a ligand. Uponreplacement with a non-native therapeutic agent and/or a ligand, thecarrier complex can, under appropriate conditions detailed below, revertback to a closed conformation, where the carrier complex now protectsthe non-native therapeutic molecule and/or the ligand from unfavorableenvironmental conditions.

In particular embodiments, a ligand can be attached to the carriercomplex or to the non-native therapeutic molecule. Where the ligand isattached to the therapeutic agent, the therapeutic agent is thenassociated to the carrier complex.

In one embodiment of the invention, alternating conformations of thecarrier complex between an open and closed conformation is induced bychanging the pH of the solution in which the carrier complex iscontained. Where the pH of the carrier complex containing solution isincreased to between about 8 and about 10, an open conformation isinduced, and where the pH of the carrier complex containing solution isdecreased to about 2 and about 7, a closed conformation is induced.

The carrier complex can consist of non-toxin proteins natively producedby C. botulinum, or the carrier complex can be produced using geneticengineering techniques. In a preferred embodiment of the invention, thenon-toxin proteins of the carrier complex are produced by C. botulinumtype A, that is, the carrier complex is derived from the multi-subunitcomplex naturally produced by C. botulinum bacteria, wherefrom thenatively associated botulinum neurotoxin subunit is removed and thusprovide a carrier complex. In one example, C. botulinum type A non-toxinproteins include an about 130 kDa non-toxin non hemagglutinin subunit,an about 52 kDa hemagglutinin subunit, an about 35 kDa hemagglutininsubunit, an about 20 kDa hemagglutinin subunit, and an about 15 kDahemagglutinin subunit. In one example, a carrier complex can compriseall of the non-toxin subunits of the multi-subunit complex derived froma type A multi-subunit complex or the invention can consist of aselection of the non-toxin subunits of the multi-subunit complex, thatis two or more of the non-toxin subunits derived from a type Amulti-subunit complex.

In another embodiment, the non-toxin subunits of the carrier complex areproduced by C. botulinum type B, that is the carrier complex is derivedfrom the multi-subunit complex naturally produced by C. botulinum typeB. C. botulinum type B non-toxin proteins include an about 130 kDanon-toxin non hemagglutinin subunit, an about 70 kDa hemagglutininsubunit, an about 33 kDa hemagglutinin subunit, and an about 17 kDahemagglutinin subunit. In a particular embodiment, a carrier complex caninclude all of the non-toxin subunits derived from a type Bmulti-subunit complex or can consist of a selection of the non-toxinsubunits, that is, two or more of the non-toxin subunits derived from atype B multi-subunit complex.

In another embodiment, the non-toxin subunits of the carrier complex areproduced by C. botulinum type C, that is the carrier complex is derivedfrom the multi-subunit complex naturally produced by C. botulinum typeC. C. botulinum type C non-toxin proteins include an about 130 kDanon-toxin non hemagglutinin subunit, an about 53 kDa hemagglutininsubunit, an about 33 kDa hemagglutinin subunit, an about 22 kDahemagglutinin subunit, and an about 17 kDa hemagglutinin subunit. In aparticular embodiment, a carrier complex can include all of thenon-toxin subunits derived from a type C multi-subunit complex or canconsist of a selection of the non-toxin subunit of the multi-subunitcomplex, that is, two or more of the non-toxin subunits derived from atype C multi-subunit complex.

The non-toxin subunits of the carrier complex can be produced by any ofthe Clostridium botulinum serotypes, thus the carrier complex cancomprise all of the non-toxin subunits of a multi-subunit complexproduced by any of the C. botulinum serotypes or the invention canconsist of a selection of two or more of the non-toxin subunits of amulti-subunit complex produced by C. botulinum. The non-toxin subunitscan all be from one particular C. botulinum type to give rise to acarrier complex, or can be a combination of non-toxin proteins ofvarious C. botulinum types. For example, and not limited to,hemagglutinin subunits from a C. botulinum type A may be combined withnon-toxin non hemagglutinin subunit from a C. botulinum type C.

For example, it is further contemplated that a carrier complex cancomprise non-toxin subunits from various C. botulinum serotypes. Forexample, and not limited to, 130 kDa non-toxin non-hemagglutininsubunits from C. botulinum type A, 70 kDa hemagglutinin from C.botulinum type B, 33 kDa hemagglutinin from C. botulinum type C, 22 kDahemagglutinin from C. botulinum type C, 15 kDa hemagglutinin from C.botulinum type A in any useful number or combination

In another embodiment, the non-toxin subunits that make up the carriercomplex are produced by E. coli. As an example, the carrier complex canbe comprised of non-toxin subunits from different native strains thatare combined to make up a variant carrier complex that is produced andisolated from E. coli.

It is to be understood that a carrier complex may be provided by eithera Clostridium or genetically transformed non Clostridium bacteria orgenetically transformed mammalian cell line such as, for example CHO orNSO. In another embodiment of the invention, the carrier complex can beproduced by a bacterium, such as E. coli, that does not produce aneurotoxin subunit. Accordingly, in such bacteria, only the non-toxinsubunits are produced by the bacterium, thus giving rise to a carriercomplex straight away, without requiring the removal of a neurotoxinsubunit. Using existing recombinant DNA technology, the bacterium, suchas E. coli, can be engineered to produce the individual subunits whichcould then be folded into the desired configuration using existingrefolding techniques.

In one embodiment of the invention, the carrier complex is produced bygrowing C. botulinum bacteria in a fermenter, under anaerobicconditions, using media comprised of soy peptone, yeast and glucose.Once grown, the multi-subunit complex can be purified from fermentationbroth using known purification techniques, such as chromatography oracid precipitation, per the Schantz method. See Preparation andCharacterization of Botulinum Toxin Type A For Human Treatment, Schantz,E. J., et al, Therapy with Botulinum Toxin, 1994; v.25: pp 41-49.Chromatographic method and system for purifying a botulinum toxin, Luo,et al. (U.S. Pat. No. 7,452,697), Animal product free system and processfor purifying a botulinum toxin, Xiang et at.(U.S. Pat. No. 7,354,740),all of which are herein incorporated by reference in their entirety.Once the multi-subunit complex, which includes the neurotoxin subunit,is purified from host cell proteins the neurotoxin subunit is isolatedfrom the non-toxin subunits and removed in accordance with the teachingsprovided herein, to provide a carrier complex.

In one aspect, there is provided a method for purifying themulti-subunit complex from a fermentation broth, thus providing asolution containing a purified form of the multi-subunit complex fromwhich the carrier complex is isolated. The pH of the multi-subunitcomplex containing solution is subsequently increased to a pH of betweenabout 8 and about 10, preferably from about pH 8.5 to about 9.5, morepreferably to a pH of about 9. The increase in pH results indisassociation of the neurotoxin subunit from the remaining non-toxinsubunits of the multi-subunit complex. In one example, the neurotoxinsubunit (now in solution and dissociated from the multi-subunit complex)is then bound to a cationic substrate, resulting in a solutioncontaining the carrier complex that is devoid of the neurotoxin subunit.The anionic substrate can be, for example, SP Sepharose HP manufacturedby GE Healthcare Life Sciences, 50HS manufactured by Poros or ToyopearlS-650M manufactured by Tosoh Biosciences.

The pH of the carrier complex containing solution, the eluate, can thenbe lowered to a pH of between about 5 and about 7, preferably to a pH ofabout 6 to induce a closed conformation. The pH is lowered to stabilizethe carrier complex, for allowing the carrier complex to remain at a pHabove 7 can result in instability of carrier complex subunits. The pH ofthe carrier complex containing solution can later be raised to induce anopen configuration to allow for the addition of a therapeutic agentand/or a ligand. In another embodiment, a therapeutic agent and/or aligand is added to the solution prior to the induction of a closedconformation, that is, while the carrier complex is in an openconfiguration and the neurotoxin subunit has been removed from thesolution. Once the therapeutic agent and/or the ligand is added to thecarrier complex, a closed configuration can be induced by lowering thepH of the carrier complex containing solution.

It is also contemplated that the neurotoxin subunit can be bound to acationic substrate. The cationic substrate can be, for example, QSepharose HP manufactured by GE, 50HQ manufactured by Poros or MacroprepHigh Q manufactured by Biorad. The neurotoxin subunit can bind to acationic substrate at a conductivity of between about 5 mS/cm and 10mS/cm at a pH of between about pH 7 and about pH 9, preferably at a pHof about 8. The carrier complex will not bind to an anionic substrate inthis conductivity range, thus the carrier complex will be in a solutionvoid of a neurotoxin subunit.

In yet another embodiment, the neurotoxin subunit is bound to ahydrophobic substrate. The hydrophobic substrate can be, for example,Butyl Sepharose HP manufactured by GE, Toyopearl Butyl 650M manufacturedby Tosoh Biosciences or Toyopearl Phenyl 650M manufactured by TosohBiosciences. The neurotoxin subunit and the carrier complex can be boundto Butyl Sepharose HP in 1M ammonium sulfate. The neurotoxin subunit canbe eluted at 0.5-0.3M ammonium sulfate. The carrier complex can beeluted at 0.2M ammonium sulfate.

In yet another embodiment, the neurotoxin subunit is bound to a mixedmode substrate. The mixed mode substrate can be, for example, MEPHypercel manufactured by Pall or Capto MMC manufactured by GE. Theneurotoxin subunit and the carrier complex can bind to the substrate inlow salt and can be eluted separately using an increasing linear saltgradient up to 1M sodium chloride, for example.

The temperature for disassociation of the neurotoxin subunit from theremaining non-toxin subunits of the multi-subunit complex can be fromabout 1° C. to about 60° C., in another embodiment of the invention, thetemperature for dissociation is between about 4° C. to about 40° C. Inyet another preferred embodiment, the temperature for disassociation ofthe neurotoxin subunit from the remaining non-toxin subunits of themulti-subunit complex can from about 32° C. to about 40° C.

The incubation time for disassociation of the neurotoxin subunit fromthe remaining non-toxin subunits of the multi-subunit complex can befrom about 1 minute to about 48 hours, in a preferred embodiment, theincubation time is from about 2 hours to about 24 hours. In yet anotherpreferred embodiment, the incubation time is from about 10 hours toabout 20 hours.

In another embodiment of the invention, the carrier complex is bound toa cationic substrate for separation from the neurotoxin subunit. Thecarrier complex can bind to a cationic substrate at a conductivity ofbetween about 10 mS/cm and 20 mS/cm at a pH of between about pH 7 andabout pH 9, preferably to a pH of about 8. The neurotoxin subunit willnot bind to a cationic substrate in this conductivity range, thus thecarrier complex can be eluted off of the substrate and can be in asolution devoid of a neurotoxin subunit.

The carrier complex can also be bound to a cationic substrate, ahydrophobic substrate or a mixed mode substrate. The cationic substratecan be, for example, Q Sepharose HP manufactured by GE, 50HQmanufactured by Poros or Macroprep High Q manufactured by Biorad. Theanionic substrate can be, for example, SP Sepharose HP manufactured byGE, 50HS manufactured by Poros or Toyopearl S-650M manufactured by TosohBiosciences. The hydrophobic substrate can be, for example, ButylSepharose FF manufactured by GE, Toyopearl Butyl 650M manufactured byTosoh Biosciences or Toyopearl Phenyl 650M manufactured by TosohBiosciences. The mixed mode substrate can be, for example, MEP Hypercelmanufactured by Pall or Capto MMC manufactured by GE.

The carrier complex can also be produced by purifying the multi-subunitcomplex from host cell proteins, followed by disassociation of thesubunits of the multi-subunit complex from one another. The subunits ofthe multi-subunit complex, including the neurotoxin subunit, can becompletely disassociated from each other using organic solvents, such asacetonitrile, for example. The concentration of acetonitrile in solutioncan be from 1% to 100%, in a preferred embodiment the concentration ofacetonitrile in solution is between about 15% and about 20%. The organicsolvent can be mixed with an aqueous buffer or water. An example of anaqueous buffer than can be used is sodium phosphate. In one embodimentof the invention, the concentration of sodium phosphate in solution canbe between 10 mM and 150 mM. The temperature for disassociation to occurcan be between about 1° C. to about 60° C., and in a preferredembodiment, the temperature for dissociation is between about 4° C. toabout 37° C.

The neurotoxin subunit, now released and no longer associated withnon-toxin subunits, is then bound to a hydrophobic substrate. Thehydrophobic substrate can be Silica C-2, Silica C-4, Silica C-8, SilicaC-10, Silica C-18, Polymeric C-4, or Polymeric C-8, for example. In oneexample, the neurotoxin subunit can bind to a hydrophobic substrate inthe presence of organic solvents equal to the percentage of organicsolvents present for dissociation.

Upon removal of the neurotoxin subunit, such as by binding to ahydrophobic substrate, some or all of the non-toxin subunits canreassociate to form the carrier complex. Reassociation can occur bydialyzing the organic solvent out of the solution, diluting the organicsolvent with an aqueous solution, evaporating the organic solvent orcentrifuging and extracting the organic phase from the aqueous phase. Inone example, following reassociation, an open conformation of thecarrier complex is induced by increasing the pH of the carrier complexcontaining solution to between about 8 and about 10 pH units, preferablyto a pH of about 9, and a non-native therapeutic molecule isjoined/associated to the complex. A closed configuration can besubsequently induced by lowering the of the carrier complex containingsolution to between about 2 and about 7 pH units, preferably to a pH ofabout 6.5, for example.

In another embodiment, the non-toxin subunits are separated from eachother using a solution high in conductivity, such as and for example,but not limited to, a solution with a high concentration of sodiumchloride. The concentration of sodium chloride can be about 0.5M toabout 2M. The incubation time of the carrier complex in said solutioncan be from about 1 minute to about 24 hours, in a preferred embodiment,the incubation time is from about 3 hours to about 24 hours. In yetanother preferred embodiment, the incubation time is from about 7 hoursto about 10 hours.

In another embodiment, the non-toxin subunits are separated from eachother using a high pH solution. The pH of the solution can be from a pHof about 7 to a pH of about 10. The incubation time of the multi-subunitcomplex in said solution can be from about 1 minute to about 24 hours.In a preferred embodiment, the incubation time in said solution is fromabout 3 hours to about 24 hours.

The carrier complex can precipitate out of solution when the pH of thesolution is in the range of about 6.5 to a pH of about 7. However,maintaining a favorable conductivity of the carrier complex containingsolution has a stabilizing effect in this particular pH range. Forexample, the carrier complex is stable in the pH range of about 6.5 toabout 7 when about 0.3M sodium chloride is added to the carrier complexcontaining solution.

In another embodiment, the non-toxin subunits are separated from theneurotoxin subunit utilizing gel electrophoresis. The multi-subunitcomplex subunits disassociate from one another with the addition ofsodium dodecyl sulfate, an anionic detergent that denatures secondaryand non-disulfide-linked tertiary structures. An electrical current runsthrough the gel allowing the subunits to migrate across the gel based ontheir molecular weight. Protein bands can be excised from the gel andsolubilized with acetonitrile. The solution is then centrifuged and thesupernatant is subsequently treated and stored in formic acid.

In another embodiment, the non-toxin subunits are separated from theneurotoxin subunit utilizing capillary electrophoresis.

Particular non-toxin subunits, so isolated from the gel run, areselected for reassociation to provide the carrier complex in accordancewith the teachings of the present disclosure. In another embodiment, anon-native therapeutic agent and/ or a ligand is added to the nonneurotoxin subunit containing solution before the non-toxin subunitsreassociate. In one example, the therapeutic agent and/ or the ligand isjoined to the complex simultaneously as the non-toxin subunitsreassociate.

Therapeutic agents can be, for example but not limited to, proteins,antibodies, DNA,

RNA, steroids, enzymes, growth factors or hormones, such as insulin.Ligands can be, for example, but not limited to virus particles,fluorescent dyes, radioactive compounds or chemical laminationcompounds. Thus in particular embodiments, the carrier complex cancomprise both a therapeutic agent and a ligand simultaneously. Thecarrier complex can also comprise only a therapeutic agent or a ligand;or can also comprise a therapeutic agent to which a ligand is attached.

In another embodiment, targeting of the non-native therapeutic agent orthe carrier complex carrying the therapeutic agent can be followed bythe addition of a detectable ligand to the non-native therapeutic agentand/or to the non-toxin subunits of the carrier complex by, for example,but not limited to, hydrogen bonding, covalent linkage or ionicinteraction.

1. An isolated Clostridium botulinum carrier complex, wherein thecarrier complex lacks a native neurotoxin subunit and said carriercomplex is capable of reversibly and controllably alternating between anopen and a closed conformation.
 2. The complex of claim 1, wherein saidcarrier complex further comprises a non-native therapeutic molecule. 3.The complex of claim 1, wherein said carrier complex further comprises aligand.
 4. The complex of claim 1, wherein said carrier complex furthercomprises a therapeutic agent and a ligand.
 5. The complex of claim 1,wherein said carrier complex is a variant carrier complex.
 6. Thecomplex of claim 5, wherein said carrier complex further comprises anon-native therapeutic molecule.
 7. The complex of claim 1, wherein saidcarrier complex comprises a non-toxin non hemagglutinin subunit and anon-toxin hemagglutinin subunit.
 8. The complex of claim 1, furthercomprising a non-native neurotoxin subunit.
 9. The complex of claim 1,wherein said carrier complex comprises a non-toxin non hemagglutininsubunit and a non-toxin hemagglutinin subunit.
 10. A method of purifyinga carrier complex derived from Clostridium botulinum, the carriercomplex lacking a native botulinum neurotoxin subunit, comprising: (a)isolating a native multi-subunit complex; (b) disassociating the nativemulti-subunit complex into its constituent subunits; (c) separating thenative botulinum neurotoxin subunit therefrom; and (d) re-associatingremaining subunits into the carrier complex, thereby producing a carriercomplex lacking a native botulinum neurotoxin subunit. (e) A carriercomplex provided by the method of claim
 10. 11. The method of claim 10further comprising the step of associating a non-native therapeuticmolecule to the carrier complex covalently.
 12. A modified organismproducing a carrier complex, said carrier complex comprising a non-toxinnon hemagglutinin subunit and a non-toxin hemagglutinin subunit, whereinsaid carrier complex lacks a neurotoxin subunit.
 13. The organism ofclaim 12, wherein the carrier complex further comprises a non-nativeneurotoxin subunit having a non-native binding moiety.
 14. A modifiedClostridium botulinum bacteria expressing a variant carrier complex,wherein the variant carrier complex lacks a neurotoxin subunit.
 15. Theorganism of claim 12, wherein the organism is a modified Clostridiumbotulinum.